lamme



(No Model.) 2 SheetsSheet 1.

B. G. LAMME. DIRECT CURRENT GENERATOR.

No. 588,279. Patented Aug..1'7, 1897.

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ATTORNEY.

(No Model.) 2 Sheets-Sheet 2.

B. G. LAMME.

DIRECT CURRENT GENERATOR.

No. 588,279. Patented Aug. 17, 1897.

WITNESSES /N VENTOI? A'rromvE Y.

UNITED STATES PATENT OFFICE.

BENJAMIN G. LAMME, OF PITTSBURG, PENNSYLVANIA, ASSIGNOR TO THEWESTINGHOUSE ELECTRIC AND MANUFACTURING COMPANY, OF SAME PLACE.

DIRECT-CURRENT GENERATOR.

SPECIFICATION forming part of Letters Patent No. 588,279, dated August17, 1897.

Application filed May 8, 1896. Serial No. 590,665. (No model.)

To aZZ whom it may concern; each short-circuited coil may be located inBe it known that I, BENJAMIN G. LAMME, thefield, and the brushes may beshifted a a citizen of the United States,residing inPittssui'iicientdistance to bring it into the field of burg, in the county of Alleghenyand State of full strength without impairing the commu- Pennsylvania,have invented a new and usetation. Such being the case, it will bereadily fullmprovementinDirect-Current Electrical understood that arelatively wide range of Machines, (Case No. 700,) of which thefolmovement of the brushes backward or forlowing is aspecification. wardis possible without substantially vary- My invention relates to dynamoelectric ing the counter electromotive force in the :omachines,andmoreparticularlytomultipolar short-circuited coils.Furthermore, if the direct-current machines having drum-armacoil hasonly one side in the field of full tures of that type in which the coilsare 10- strength and the entire load be thrown oif the cated'in slots inthe core. machine, the short-circuiting efiect will re- My invention hasfor its object to provide main approximately the same as before, pro- .5a machine of the general character specified vided the machine isdesigned for a small disin which self-induction in the armaturecoils,tortion of the field by the armature-current. which are short-circuitedat the brushes, shall On the other hand, with the usual construcbereduced to the smallest practicable limits, tion of machine in whichboth sides of the and one in which sparking is substantiallyshort-circuited coil are located in a field of :0 obviated withoutinvolving delicate and accusubstantially half the full strength thefringe rate adjustment of the commutator-brushes. may rise in strengthto almost that of the full It is generally understood that satisfactoryfield when the load is thrown off, and the shortcommutation of currentsof large volume incircuiting effect will consequently be very volves thegeneration of a counter electromonearly doubled.

:5 tive force in the coils which are short-cir- Substantially the sameresult may be secuited at the brushes. In order to secure this cured asregards the adjustment of the comresult in machines of usualconstruction, the mutator-brushes if instead of varying the brushes aremoved forward until both sides windingof the armature from that usuallyof the short-circuited coils are located in the employed thefield-magnet be provided with o fringe of the magnetic field. If thebrushes means whereby the width of the fringe at are moved a greaterdistance, so that the alternate pole-pieces is increased in width. short-circuited coils are in a field of full In theaccompanyingdrawings,Figure lis strength, the counter electromotiveforce of a rear end elevation, partially diagrammatic, the coil will bein excess of that desired and of a machine constructed in accordancewith 5 the commutation will not be satisfactory. In my invention; andFig. 2 is a diagrammatic 8 5 machines in which the magnetic field isvery development of the armature and the commustrong and the air-gapbetween the armature tator of such machine. Fig. 3 is a view simiandpole-pieces is small the magnetic fringe lar to Fig. 10f amodification.Fig. 4cis a face may be very narrow, so narrow in fact that view of oneof the pole-pieces of the machine .0 the distance between the positionof no field shown in Fig. 3 provided with a shoe. 0

and that of full field may be so small as to Referring now to Figs. 1and 20f the drawnecessitate a very delicate adjustment of the ings, 1 isthe field-magnet frame of the mabrushes in order to secure the desiredcounter chine, 2 the pole-pieces, and 3 the field-magelectromotive forcein the shortcircuited netc-oils. 4isthe armature, which isof usual 5coils. If, however, each of the armatureconstruction except as regardsthe dimensions 9 5 coils be of such dimensions as to embrace a of thegenerating-coils 5 with reference to portion of the periphery of thecore which the field-magnet pole-pieces. 6 is the comis either greateror less in Width than the mutator-cylinder, and 7 the brushescooperdistance between the centers of adjacent ating therewith. Thearmature-coils 5 are 0 fieldmagnet pole -pieces, one side only oflocated in slots in the periphery of the core,

as indicated in Fig. 1, there being two conductors in each slot, andeach of these coils embraces a portion of the periphery of thearmature-core which is less than the distance between the centers of thefield-magnet polepieces. With such a construction it will be readilyseen that when the side of any coil is just coming under the edge of apole-piece the other side will be either completely under the adjacentpole-piece, and consequently subject to the full strength of themagnetic field, or else it will be in a position of no magnetic field.This construction, as has already been pointed out, renders it possibleto so adjust the commutator-brushes that the coil which isshort-circuited through any particular brush will have one side ineither a partialor a full magnetic field and the other side in aposition of no field, and that a considerable movement of the brushesmay be effected in either direction without materially affecting thiscondition of the coil. A further important advantage incident to thisconstruction resides in the fact that neither side of a short-circuitcdcoil lies in the same slot with a side of any other short-circuitedcoil, whereas in the usual construction, in which the space between thesides of each coil is equal to the distance between the centers ofadjacent pole-pieces, adjacent sides of two shortcircuited coils lie inthe same slot, a construc tion which is productive of a considerableamount of self-induction and consequent sparking at the brushes. lViththe arrangement such as I have shown in Figs. 1 and 2 above describedthis self-induction, which has heretofore been present by reason of therelative location of the adjacent sides of the short-circuitcd coils, isreduced by about onehalf.

The improved results incident to the 0011- struction above described mayalso be ob tained by employing coils which embrace spans of greaterwidth than the distance between the centers of adjacent field-magnetpole-pieces, and I regard such. a construction as within my invention.

Referring now to Fig. 3, the field-magnet frame 1, pole-pieces 2, andcoils 3 are substantially the same as the corresponding part s in Fig.1, except that the field-magnet has siX pole-pieces instead of four. Inthe machine shown in Fig. 3, however, the armature a is provided withcoils 5, each of which embraces a portion of the armature-core which isequal to the distance between the centers of adjacent pole-pieces, thisbeing the usual construction. In order to secure a relation between theshortcircuitcd armature coils and the field which will obviate thenecessity of an accurate adjustment of the brushes with this old form ofmachine, I provide the alternate pole-pieces with magnetic pole-shoes 8.These shoes, as shown in Fig. 5, surround the inner ends of thepole-pieces and are preferably flush with their faces. \Vith thisarrangement the magnetic field will be so adjusted with reference to thearmature-coils that substantially the same variation in adjustment ofthe brushes may be effected as that hereinbefore described withoutdisturbing the relation between the short-circuitcd coils and themagnetic field.

I claim as my invention- 1. The combination with the field-magnet of adirect-current electrical machine, of a commutator and a slottedarmature-core provided with a winding comprising a set of coils each ofwhich embraces a space which is less than the distance between thecenters of ad jacent field-magnet pole-pieces and has its terminalsconnected to segments of the commutator cylinder which are spanned bybrushes oi the same sign, whereby the desired counter electromotiveforce in the short-cir cuited coils may be readily secured.

2. In a direct-current electrical machine, a multipolar field-magnet incombination with a commutator and a drum-armature provided with a set ofcoils the distance between the sides of each of which is either greateror less than the distance between the corresponding edges of adjacentpole-faces, and each of which is connected at its ends to segments ofthe commutator-cylinder which are spanned by brushes of the same sign,whereby the desired counter electromotive force in the shortcircuitedcoils may be readily secured.

3. A direct-current electrical machine havin g an armature-core providedwith slots and a winding comprising two sets of coils located in saidslots, the sides of the several coils which are short-circuitcd at thebrushes being in separate slots with reference to each other, wherebythe self-induction in such coils is reduced.

In testimony whereof I have hereunto subscribed my name this 5th day ofMay, A. D. 1896.

BENJ. G. LAMME.

lVitnesses:

WESLEY G. CARR, HUBERT C. TENER.

